production · inflow
Standing IPR (Flow-Efficiency Modified)
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Inputs
STB/d
—
psi
psi
Description
Computes inflow rate from Standing's (1970) flow-efficiency-modified form of Vogel's equation, which extends Vogel's solution-gas-drive IPR curve to wells with significant skin (damage or stimulation). Flow efficiency (FE) is a direct input — sourced from the Skin Factor calculator's own FE output, the same re-enter-the-value pattern already used between Rod Pump Efficiency and Rod Pump Displacement — rather than being re-derived from skin here.
Variables
| Symbol | Unit | Description |
|---|---|---|
| q | STB/d | Inflow Rate |
| AOF | STB/d | Absolute Open Flow (actual well) |
| qmax | STB/d | Absolute open flow potential the well would have at zero skin (FE = 1) — the same qmax used in Vogel's equation. |
| FE | — | Flow efficiency of the actual (damaged or stimulated) well relative to an ideal zero-skin well. Not derived internally — run the Skin Factor calculator first and carry its FE output in here (see relatedCalcs). |
| Pwf | psi | Flowing bottomhole pressure at which to evaluate the inflow rate. |
| Pr | psi | Average reservoir (static) pressure, at or below the bubble point for the Vogel-based form to apply. |
Assumptions
- The reservoir is at or below the bubble point with solution-gas drive as the dominant mechanism, same as Vogel's underlying assumption
- FE is a representative, current value for the well — typically sourced from a recent pressure transient test's skin factor via FE ≈ ln(re/rw)/(ln(re/rw)+S)
- qmax is the well's ideal (zero-skin) AOF potential, consistent with how it would be used in an unmodified Vogel calculation
Limitations
- Not valid above the bubble point — same restriction as the underlying Vogel equation
- FE is a single lumped correction for near-wellbore skin; it does not distinguish which mechanism (mechanical damage, partial completion, non-Darcy flow) is responsible
- Very large FE (heavily stimulated wells) can push the quadratic term negative at high drawdown before Pwf reaches zero — flagged but not physically capped by this calculator
Use Cases
- → IPR for damaged or stimulated wells: Predict producible rate at a target Pwf for solution-gas-drive wells with known non-zero skin, where plain Vogel would misrepresent the true curve.
- → Post-stimulation IPR comparison: Compare pre- and post-treatment IPR curves using FE from Skin Factor before and after a workover, quantifying the production uplift.
- → Nodal analysis with a damaged completion: Generate the FE-corrected reservoir-side IPR curve for nodal analysis when the well is known to carry significant skin.
Related Calculations
Region Notes
Permian Basin
Post-frac Wolfcamp/Bone Spring wells with strongly negative skin (FE well above 1) commonly use the Standing-modified IPR to represent the AOF improvement from stimulation more accurately than plain Vogel.
Global
Always source FE from a current pressure transient test — skin changes over a well's life (scale, stimulation decline), and a stale FE will misrepresent the current IPR curve.
References
Primary source
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